Although JP-A 11-140073 and JP-A 2002-212063 disclose a method for producing (S)-2-(1,6,7,8-tetrahydro-2H-indeno[5,4-b]furan-8-yl)ethylamine hydrochloride by means of asymmetric reduction from (E)-2-(1,6,7,8-tetrahydro-2H-indeno[5,4-b]furan-8-ylidene)ethylamine hydrochloride as starting material, both methods are not enough as an industrial production method in which the formation of side products is suppressed and high-purity crystals of (S)-2-(1,6,7,8-tetrahydro-2H-indeno[5,4-b]furan-8-yl)ethylamine hydrochloride are produced with high yield. In particular, problems are to control the side products represented by the following formulae (III′) and (IV′).

On the other hand, dimerization of benzofuran compound under the presence of Pd-catalyst is described in Liebigs. Ann. Chem., 10,945 (1989) and J. Chem. Soc. (A), 1324 (1968). However, these cases are the dimerization by binding of two aromatic rings, and the structures of their dimers are different from those of dimers formed by the reaction between aromatic ring and benzyl position, like compound represented by the above formula (IV′). In addition, J. Chem. Soc. D, 736 (1970) discloses that oxidation of benzyl position of benzofuran compound takes place under the presence of Pd-catalyst, but formation of dimer is not described therein.